Transmission gear having an automatically variable transmission ratio



M y 1939- v A. VINCEINZCVDNI 2,159,462

TRANSMISSION GEAR HAVING AN AUTOMATICALLY VARIABLE TRANSMISSION RATIO Filed March 24, 1937, 2 Sheets-Sheet l May 23, 1939.

A. VINCENZONI 2,159,462 TRANSMISSION GEAR HAVING AN AUTOMATICALLY VARIABLE wamsuzssrou RATIO 2 Sheets-Sheet 2 Filed March 24, 1937 Patented May 23, 1939 UNITED STATES PATENT OFFICE p TRANSMISSION Gm HAVING AN AUTO- HATICALLY VARIABLE TRANSMISSION RATIO Alvaro Vineensoni, 'lerni, Italy Application March 24, 1937, Serial No. 132,836

In Italy April 1, 1938 1 Claim. (CI. 14-11:

1 members being carried by a resilient member .which tends to hold it in the position of greatest eccentricity but is deformed in accordance with the resistance to be overcome and thus varies the relative eccentricity of the two members. Hitherto, in a gear of this kind the driving and driven members have consisted of toothed wheels driven by achain and the relative displacement of the two-toothed wheels has been affected when resistance occurs owing to the additional stress produced on the chain which causes the wheels to approach one another and thus eilects a reduction in the transmission ratio. With this arrangement a tensioning pulley'is in order to take up the slack in the chain and further the member which is carried by the resilient member must be the driving member and it is impossible to invert the driving and driven members. These disadvantages, among others. are obviated by the present invention.

According to the invention, the driving and driven members are parallel shai'ts one of which is mounted so asto be caused to approach the other by increased load against the action of a control spring. With this arrangement the drive need not necessarily be eil'ected by means of a chain and further either the driving member or the ,tiriven member may be the member which is resiliently supported.

According to a preferred form of construction, one end of each drag link is pivoted by means of a pin near to. the periphery of a disc which is rigidly connected to one of the shatts, while the other end is slidably guided, in or near the suitably formed periphery oi a disc which is rigidly that the individual links come into action in succession and are then disengaged, by over running the disc, as soon as the next link has arrived in a position in which it transmits the power. In this way, the angle subtended by two successive points of engagement and the, angular velocity of the one shaft relatively to the other shaft is varied in with the relative is eccentricity of the two shafts.

connected to the other shaft, in such a manner A transmission gearing in accordance with the invention is illustrated diagrammatically and by way of example in the accompanying drawings. in which Fig. 1 is a diagram showing the two rotating 5 discs'with five connecting links between them in two difierent relative positions, the concentric position being illustrated in dotted lines and the eccentric position in full lines;

Fig. 2 is a vertical section through the plane of the two shafts; I

Fig. 3 is a part section on a larger scale through the central plane of the disc, the connecting links being shown in side elevation;

Fig. 4 is a corresponding vertical cross section of the same disc and through the operating end of a connecting element;

Fig.5isaviewonthesaidedgeandthesaid connecting element partially sectioned in a longitudinal sense;

Fig. 6 shows a portion of a section like Fig. 2 with back pedalling brake;

Fig. 7 shows a detail of the mechanism according to 6;

Fig. 8 shows the device according to Fig. 5 5 adapted for bicycles with back pedalling brake.

In the form of execution shown in the drawings the disc I, fixed in the shall; I, is provided with two edges 2 which have on their inner opposite sides an arched groove, the centres of each arch being at the same distance from the axis of rotation.

In the grooves 3 roll the balls 4 carried by guide blocks 5 on the tapered head 6 of the connecting rods 1, which have on their opposite end the boxeslbymeansofwhichtheyareswingingon the pins 0', which are fixed on the periphery of the disc 9;small springs ll tend to pushthe whole 01' the blocks 5 with the balls 4 towards the.

ends of the heads 6 which are enlarged.

The shafts i' and t are mounted on the bearings II and.

Thebearing llisintegralwiththebase l2,

whereas the bearing ll isslidablesoastoallow the displacement of the shaft 0' in 811 eccentric position relative to the shaft l and is guided in the slide it which also is integral with the base the heads of the rods 6 and the grooves 3 by thepush of the ,springs I6 and by'the friction of the balls between the wedged surfaces and the grooves 3.

The disc I carries along the rods I in its motion and the rods draw along the disc9.

If the relative position of the two shafts I' and 9' is the concentric position, the connecting rods I will maintain their angular position unchanged in respect of the discs I and 9 during rotation.

If their relative position is an eccentric one, a series of oscillations of the. rods I on their pins 8' and on the other side on the balls 4 will take place during the rotation.

Thus the continuous connection between the disc I and the disc 9 is ensured whatever the relative position of their axes of rotation may be.

'Figure 1 shows how in the coaxial position all of the connecting elements I maintain equal distances between the engagement points of these balls 4 on the periphery of the disc I. On the contrary in the eccentric positions distances of the said engagement points should be varying between a minimum and a maximum at any-- of the rod heads Ii relative to the constant pcripheric speed of the disc I. In view of these variations of speed of the head Ii relative to the periphery of the disc'I, it occurs that on the side towards the eccentric shaft 9' theperipheral speed of the disc I is higher than the speed of the heads 6, and vice versa on the opposite side this speed is lower.

Therefore in the first zone an automatic engagement will take place as the balls v4 will be clamped between the edges 2 and the conical heads 6. The rod being engaged will take up the peripheral speed of the disc I and will therefore transmit a speed acceleration to the disc 9.

In this manner a continuous series of impulses will be transmitted, and the zone of engagement between the heads 6 'and the disc I will be shorter,- with consequent stronger acceleration, the higher the degree of relative eccentricity between the two axes of rotation. Outside of the zone of engagement, the speed of the heads 6 being higher than the peripheric speeds of the disc I, the balls 4 are automatically disengaged and move freely in the grooves 3;

I It will be evident from the drawings that when the rods are engaged on the side of the eccentricity the traction stress exercised by the disc I on the rods I is divided in two forces of which the one has ,a tangential direction and transmits.

the rotatiomwhereas the other is directed radially and equilibrated by the reaction of the bearings III and II which are supported on the base I2 also decreases the ratio of acceleration of the system of transmission until the equilibrium between the transmission ratio and the resistance to be overcome is obtained without the intervention of further controlling members.

The mechanism as described and shown in the Figures 1 to 5 is for free wheel bicycles. In this case the disc I will only transmit the movement when rotating in the sense of the arrow in Fig. 3, whereas when rotating in the opposite sense no transmission takes place. But in the case of application of a back pedalling brake to the bicycles a transmission is necessary. In the Figures 6 to 8 of the drawings there is therefore shown as an example a mechanism with automatically variable ratio of transmission, in which when the disc I is rotated against the sensed the arrow I5 a transmission of this movement to the disc 9 is also obtained at such a degree as is, for example, suflicient in bicycles with back pedalling brake.

In the form of execution shown in Fig. 6 the disc I, which is at a little distance from the support I0, bears the disc I! having a projecting edge I'I' capable of being pushed at contact into the blocks 5 and to exercise a strong pressure on these blocks.

The disc I1 revolves together with the disc I, being connected to it by three or more pins I9 placed equidistantly and concentrically around the shaftfixed on the said disc I, and corresponding to bores in the disc I'l.

With the pins I8 are alternated springs I9 engaged into holes of the disc I and pressing on the disc II. Between the disc I1 and the support III there are placed 3 or more balls 20 guided by a ring 2I rotatable on the shaft I.' On the adjacent face of the support III, in a position corresponding to the balls 29 and in the same number, helicoidal surfaces 22 are provided having' the shape illustrated in Fig. '7 in which for sake of clearness they are developed.

In the form of execution shown in Fig. 8, the

small connecting'rods are provided on their heads with surfaces inclined in two senses, that is to say towards their end at 9 and towards their stem at Ii.

The operation of the device in this latter form is as follows:

When pedalling in the normal sense, the disc I rotates in the sense of the arrow I5 in Fig. 6 corresponding to the arrow 23 in Fig. 7 and the whole mechanism is operating as already described with reference to the Figures 1 to 5 as the disc Il under the pressure of the springs I9 compels the balls 20 to remain on the low ground of the surfaces 22 and therefore detached from the disc I and not pressing on the disc I! (full lines in Fig. 7). The edges II, as shown also in Fig. 6, are not contacting with the blocks 5. If the disc I is stopped the disc 9 is capable to rotate by inertia. When pedalling backwards,

the disc I- rotates in. the opposite sense, that is to say the disc II in Fig. 7 rotates in the sense of the arrow 24 and being pressed by the springs III on the balls 29 compels the balls to rise on the high portions of the surfaces 22. The balls 20 will push the disc I'I against the action of the springs I9 to press edge I? on the blocks 5.

By the action of this pressure the guide-blocks 5 are dragged by the disc I! in the sense of the arrow 25 of Fig. v8 and overcome the force of the springs I6. The balls 4 are squeezed between the flanges 2 of the disc I and the conical surfaces 9' of the connecting rods I, thereby transmitting movement in this sense of rotation for some portion of the revolution, which is suificient for example to apply the brake in bicycles with back pedalling brake.

' 1 the edges l'l' free the blocks 5 which under the action of the springs It will return in their normal position.

What I claim is:

A variable speed gear comprising a rotary driving member, a rotary driven member and means connecting them comprising a plurality of drag links in which the ratio of transmission is antomatically varied by relative displacement of the two members from a position of maximum eccentricity, corresponding to a maximum ratio of transmission, through intermediate eccentric positions into a concentric position, a spring carrying one of said members and tending to hold it in the position of greatest eccentricity which is deformed in accordance with the resistance to be overcome and thus varies the relative eccentricity of the two members, the driving and driven members being parallel shafts one of which is so mounted as to be caused to approach the other by increased load against the action of the said spring, said drag links being so'constructed and arranged that either thedriving or the'driven member may be supported by the resilient member, and means upon one of said members for gripping said drag links.

ALVARO VINCENZONI. 

